From 45a63d3ff611b1412f9d811cd328b648bada5ca2 Mon Sep 17 00:00:00 2001
From: Mitsunori Komatsu <komamitsu@gmail.com>
Date: Tue, 31 May 2016 01:53:14 +0900
Subject: [PATCH] Add message argument to `assert_eq` macro

---
 src/libcore/macros.rs                        | 13 ++++++++++++-
 src/test/run-pass/assert-eq-macro-success.rs |  3 +++
 2 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/src/libcore/macros.rs b/src/libcore/macros.rs
index a40608b0762d6..376d2792c445c 100644
--- a/src/libcore/macros.rs
+++ b/src/libcore/macros.rs
@@ -94,7 +94,18 @@ macro_rules! assert_eq {
                 }
             }
         }
-    })
+    });
+    ($left:expr , $right:expr, $($arg:tt)*) => ({
+        match (&($left), &($right)) {
+            (left_val, right_val) => {
+                if !(*left_val == *right_val) {
+                    panic!("assertion failed: `(left == right)` \
+                           (left: `{:?}`, right: `{:?}`): {}", left_val, right_val,
+                           format_args!($($arg)*))
+                }
+            }
+        }
+    });
 }
 
 /// Ensure that a boolean expression is `true` at runtime.
diff --git a/src/test/run-pass/assert-eq-macro-success.rs b/src/test/run-pass/assert-eq-macro-success.rs
index 9662e1ff33d11..3110e22d5da13 100644
--- a/src/test/run-pass/assert-eq-macro-success.rs
+++ b/src/test/run-pass/assert-eq-macro-success.rs
@@ -16,4 +16,7 @@ pub fn main() {
     assert_eq!("abc".to_string(),"abc".to_string());
     assert_eq!(Box::new(Point{x:34}),Box::new(Point{x:34}));
     assert_eq!(&Point{x:34},&Point{x:34});
+    assert_eq!(42, 42, "foo bar");
+    assert_eq!(42, 42, "a {} c", "b");
+    assert_eq!(42, 42, "{x}, {y}, {z}", x = 1, y = 2, z = 3);
 }